1. Field of the Invention
The present invention relates to a measuring apparatus to determine the dimensions of an object in three dimensions, e.g. a tool used in a machining apparatus, an electrode of an electroerosive machining apparatus etc. The apparatus of the invention comprises a base plate member with a measuring object station adapted to fix an object to be measured such that it can be rotated but is immovable in radial and axial directions. Besides the object receiving station a measuring carriage assembly is mounted, including a guiding column and a measuring carriage slidable along the guiding column e.g. up and down. The measuring carriage incorporates a measuring rail slidably mounted in a direction perpendicular to the extension of the guiding column and bearing at one of its end a measuring calliper assembly.
2. Prior Art
In a known apparatus of this kind an object, e.g. a tool, is fixed in the object receiving station and the measuring carriage is moved along the guiding column into a suitable height position. Then the measuring rail is displaced towards the object to be measured until the sensing surface of the calliper head provided at the end of the measuring rail touches the object. The value of displacement of the measuring rail is recorded and therefrom a first dimension, e.g. a horizontally extending dimension, can be derived. To determine a second dimension, e.g. a horizontally extending dimension, the measuring rail is displaced towards the object to such an extent that it overlaps the object. Then the measuring carriage is lowered until another sensing surface of the calliper head touches the object again. The height position of the measuring carriage is recorded and therefrom said second dimension can be derived.
Because the moment at which the sensing surface of the calliper head touches the object can not be determined easily, or because an intuitive displacement of the measuring rail towards the object until the sensing surface of the calliper head touches the object would be much too inaccurate, it is well known to use calliper means, e.g. inform of measuring gauges, which record and display a contact with the object to be measured sufficiently accurately.
Already known measuring callipers work unidirectionally linear, i.e. a linear dimension variation in one given direction (and only in this direction) is proportionally transformed into a measurement value displayed by the measuring apparatus operatively coupled to the measuring calliper. Therefore, in order to determine the dimension or a dimensional divergence or a variation in dimension of a work piece in two different directions, either the utilized measuring apparatus including the measuring calliper had to be rearranged and readjusted again, or one had to utilize two measuring set-ups working independently from each other. Such proceeding resulted in an increased expenditure of working hours and/or financial investment.